No Batteries Required: Self-powered Devices on the Horizon

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COLLEGE STATION, Texas, December 4, 2008 (ENS) - A self-powering cellphone that converts the sound waves of the user's speech into the energy it needs to keep running - without a battery charge - is being made possible by the work of a scientist at Texas A&M University.

Tahir Cagin, a professor in the Department of Chemical Engineering at Texas A&M, is a nantechnology specialist who has discovered a type of material that can covert energy at a 100 percent increase when manufactured at a very small size.

Cagin and his partners from the University of Houston are pioneers in the new field of power harvesting. They are developing self-powered devices that do not require replaceable power supplies.

"Even the disturbances in the form of sound waves such as pressure waves in gases, liquids and solids may be harvested for powering nano and micro devices of the future if these materials are processed and manufactured appropriately for this purpose," Cagin said.

Key to this technology are piezoelectrics, explained Cagin, who is a past recipient of the prestigious Feynman Prize in Nanotechnology.

Derived from the Greek word "piezein," which means "to press," piezoelectrics are materials, such as crystals or ceramics, that generate voltage when a form of mechanical pressure is applied.

Cagin and his team have found that a certain type of piezoelectric material can covert energy at a 100 percent increase when manufactured at a specific size - 21 nanometers in thickness.

When the materials are constructed larger or smaller than this specific size they show a significant decrease in their energy-converting capacity, he said.

Cagin's findings, which are detailed in an article published this fall in "Physical Review B," the scientific journal of the American Physical Society, could have profound effects for low-powered electronic devices such as cell phones, laptops, and personal communicators used by everyone from the average consumer to law enforcement officers and to soldiers on the battlefield.

Discovered by French scientists in the 1880s, piezoelectrics were first used in sonar devices during World War I. Today they are found in microphones, quartz watches, and cigarette lighters in automobiles.

Some night clubs feature dance floors built with piezoelectrics that absorb and convert the energy from footsteps in order to help power lights in the club.

Piezoelectric generators can be placed on sidewalks or in car lanes to transform the mechanical power to electrical power.

While advances in those applications are progressing, piezoelectric work at the nanoscale is a relatively new endeavor with different and complex aspects to consider, said Cagin.

"When materials are brought down to the nanoscale dimension, their properties for some performance characteristics dramatically change," said Cagin.

"One such example is with piezoelectric materials," he said. "We have demonstrated that when you go to a particular length scale - between 20 and 23 nanometers - you actually improve the energy-harvesting capacity by 100 percent."

"We're studying basic laws of nature such as physics and we're trying to apply that in terms of developing better engineering materials, better performing engineering materials.

Battery life is a major concern for popular mp3 players and cell phones that are required to perform an ever-expanding range of functions. But beyond consumer convenience, self-powering devices are of interest to federal agencies such as the Defense Department.

The Defense Advanced Research Projects Agency has investigated ways for soldiers in the field to generate power for their portable equipment through the energy harvested from walking. And sensors, such as those used to detect explosives, could utilize a self-powering technology that would eliminate the need for the testing and replacement of batteries.

{Photo: Cellphones may soon be powered by the speech of the user. (Photo by Myselia)}